Tom Chivers is the Telegraph's assistant comment editor. He writes mainly on science. Not a poet - that's the other Tom Chivers. Read older posts by Tom here.

Not all senior Conservatives have David Cameron's moralising attitude towards the porn industry

Pornography. Dreadful stuff. Never touched it myself, obviously. Terrible. All those naked people doing those unhygienic things. Who wants to see that? Not me. And the plots are all so dreadfully unconvincing. I'm told. By others. So obviously I'm right behind David Cameron's move to make it completely impossible for any youth ever to see anything naughty on the internet. It's something to do with a filter that detects any glass stiletto heels, women called Loxxy, or 32-year-olds in school uniform, and sets off a "porn klaxon" which can be heard two streets away, shaming the filthy child away from a life of hairy-palmed, myopic sin.

It's not, obviously. What he's actually doing is not completely clear, and depends on where you get your news from. It's been described in some quarters as an "opt-in" system, where customers will have to tell their internet providers that, yes, thank you, we do want access to AnatomicallyImplausible.xxx. But that seems not to be the case. A source at one major ISP said: "Customers will be asked if they want parental controls, and told how to use them. They can then choose, at home, in private, what sort of sites they want to block (gambling for example) but they do not need to tell us anything nor will we ask about explicit sites." So it's opt-in parental controls, not opt-in porn; the default setting is still all porn, all the time. According to James Firth of the blog SlightlyRightOfCentre.com, "ISP bosses are livid" at David Cameron's headline-grabbing stunt, saying that discussions with the Department of Education are still ongoing, and that they are focused on consumer education and choice, and making safeguards more accessible and easier to use. His blog is well worth a read.

Whatever the Cameron Pornblock turns out to be, the arguments it has inspired are instructive. Britain has an uncomfortable relationship with pornography and nudity, unlike most of our European cousins: I remember as a child being utterly startled the first time I watched telly in France and saw actual naked ladies on a shampoo advert. But now, largely thanks to the internet, it's here, it's legal, it's easily accessible, and since our children tend to be better at using the computer than we are, we worry that they're, you know, looking at it.

It's an understandable worry, of course. But we want to think about it seriously, and not leap on bandwagons or jump at shadows. I don't think anyone is seriously arguing that children should watch more porn, but is there any evidence that a) they're watching more now than they used to and b) it's doing them harm?

It's hard to believe that the internet hasn't led to more children watching porn, what with there being so many children using the internet and so much porn on it, but I can't find any serious evidence that it has led to a major upsurge. In the US, the Youth Internet Safety Survey (YISS), a "nationally representative, cross-sectional telephone survey of 1501 children and adolescents (ages 10–17 years)", found that the "vast majority (87%) of youth who report looking for sexual images online are 14 years of age or older, when it is developmentally appropriate to be sexually curious." Children under 14 who have intentionally watched porn, it says, "are more likely to report traditional exposures, such as magazines or movies" – just like in the good old days. "Concerns about a large group of young children exposing themselves to pornography on the Internet may be overstated", it concludes.
An analysis by the Queensland University of Technology, published last year in the Australian Journal of Communication, found something similar: "studies… suggest that current generations of children are no more sexualised than previous generations" and "young people who seek out sexualised representations tend to be those with a pre-existing interest in sexuality" – ie it's not that exposure to sexual images causes children to become interested in them, it's that the natural process of adolescence makes children interested in sex, whereupon they seek out these images.

However, that's not to say that we shouldn't try to protect children from exposure to pornography. Does it do harm to those children who do see it, even if it's not an epidemic? The YISS raised concerns: "Those who report intentional exposure to pornography, irrespective of source, are significantly more likely to cross-sectionally report delinquent behavior and substance use in the previous year." It adds that users of online porn as opposed to offline were more likely to show clinical symptoms of depression and "lower levels of emotional bonding with their caregiver". More research is needed, it says, although it makes no claim of causation rather than correlation. The Australian study found that "pornography is not addictive" and that "age of first exposure to pornography does not correlate with negative attitudes towards women"; a study in the journal Aggression and Violent Behavior concluded that "it is time to discard the hypothesis that pornography contributes to increased sexual assault behavior". That's not to say that there are no harms: harm is a very broad word. But however you define it, the evidence for pornography being harmful is not strong.

(An interesting side-note, by the way, is that a couple of studies – including the Queensland one – suggest that adult concern about child sexualisation might have its own problems: according to the Queensland report, adolescents "are not innocent about sexuality, and that a key negative effect of this knowledge is the requirement for them to feign ignorance in order to satisfy adults’ expectations of them". Another talks about the "fetishisation of innocence". But that's another debate.)

I should say this, for the avoidance of all doubt: there are excellent reasons for not approving of porn, not least the exploitation of the women who work in the industry. And I'm obviously not arguing in favour of children watching it. Of course parents should try to keep inappropriate material away from young children, and supervise their internet use. But they needn't be fretting every hour of the day that beloved Tarquin will see a stray nipple and be driven to wild perversion by it. Adolescent boys will seek out pictures of naked women when they start getting naked women on the mind. Any government legislating against that might as well issue a decree against water flowing downhill.